Intro Flashcards
epidemiology
the study of disease dynamics in populations
Disease is a (random/not random) event?
Disease is NOT a random event!
3 Components of One Health
- Human
- Animal
- Environment
3 Categories of the SIR Infection Model
- Susceptible
- Infectious
- Removed (recovered or dead)
Host-Agent-Environment Triad
interaction of all three determines whether or not disease is going to occur
Characteristics of the Host
age, prior exposure, susceptibility, co-infection, immune status
Characteristics of the Agent
toxicity, virulence, infectivity, antibiotic susceptibility, ability to survive outside the body
Characteristics of the Environment
climate, physical structures, population density, societal structure
YOPIC
Young, Old, Pregnant, ImmunoCompromised
Host Interventions
immunize, treat, isolate, better nutrition
Agent Interventions
eradicate or genetically modify
Environment Interventions
improve housing quality/ventilation, water, sanitation
4 Primary Tools for Infectious Disease Control
- Identification of Cases
- Isolation of Cases
- Quarantine of the Exposed
- Vaccination of the Susceptible
isolation
occurs when you are already clinically infected
quarantine
done when you are exposed but not yet a case
Are isolation and quarantine interchangeable?
no
Which poses the greatest risk: pre-clinical, sub-clinical, or clinically evident disease?
Both pre- and sub-clinical
Three Reasons Why Pre and Sub Clinical Cases Pose Greatest Risk
- Infected and shedding
- Difficult to detect
- Still active in the herd/community
5 Ways Epidemiology Research works with Infectious Disease Control
- Drugs for disease prevention
- Education/Sanitation and Hygiene
- Vaccines to prevent transmission
- Vaccines to prevent infection
- Vector Control
What three things do you need to know for development of an effective disease control program?
- Causes of the Disease
- Impact of the Disease
- Natural Course of the Disease
Causes of Disease
includes etiology, pathophysiology, and risk factors
2 Categories of Models of Disease Causation
- Deterministic
- Multi-factorial
Koch-Henle Postulates (4)
deterministic model
[Rothman’s] Casual Pies
multifactorial; not just simply the presence of an agent causes disease, there must also be other factors to create disease
Web of Causation
entangled spider web as all causative factors are interconnected and there rarely is one causative factor to any disease or illness
Intrinsic Host Factors
genetic predisposition, epigenetics, physiological state, immune status (exposed vs naive), co-morbidities
Extrinsic Host Factors
socio-economic/husbandry factors
Environmental Factors
air quality, ventilation, sanitation
4 Ways We Measure the Impact of a Disease
- Number of cases
- Ease of transmission
- Economic impact
- Social impact
prevalence
all of the existing cases at a point in time; how big is the problem?
incidence
number of new cases that occur over a period of time; how likely is someone going to develop the disease?
morbidity
sick
mortality
death
sequelae
essentially consequences/what happens next
Factors in the Natural Course of the Disease
reservoirs, how is the agent introduced into the population, period of infectivity, severity of disability, length of immunity, potential for long-term consequences
Reasons we should know how to critique biomedical literature?
clients ask us questions, they find stupid stuff on the internet, product reps try to sell us things, etc
Hierarchy of Evidence (8)
4 Basic Study Designs
- Cross Sectional
- Case Control
- Cohort
- Clinical Trial
Which basic study designs are prospective, meaning they look forward in time?
cohort, clinical trials
Which basic study designs are retrospective, meaning they look backward in time?
cross-sectional, case-control
Relative Risk
measure of association in prospective studies
Odds Ratio
measure of association in retrospective studies
cross-sectional study
survey a defined population at a single point in time; aka prevalence survey
Benefits of Cross-Sectional Studies
inexpensive, quick, useful for common diseases
Case Control Study
compare exposures in cases and controls to and determine the relationship with disease
Limiting Factor in Cross Sectional Studies?
you can only determine association, not cause
Cohort Study
population free of disease to begin with is unexposed/exposed to in order to estimate the incidence of the disease
Can retrospective cohort studies exist?
No, this is tricky so pray she doesn’t ask about it because it doesn’t make sense to me (retrospective cohorts are still prospective studies)
clinical trial
allocate groups to control and one or more health-related interventions to evaluate the effects on outcome after exposure
Critique Questions for Epidemiology Studies
-Reliability of Diagnostic Test?
-Study design?
-What population? Was it representative?
-What determined exposure?
-Case definition? Subjective, objective?
-Association vs. Cause and Effect?
-Internal and External Validity
-Statistical analysis?
Internal validity
Are conclusions consistent with results?
External Validity
Do the findings apply to the reference population?
selection bias
a kind of error that occurs when the researcher decides who is going to be studied
information bias
distortion in the measure of association caused by a lack of accurate measurements of key study variables (or maybe even too many but irrelevant)
Confounding Factors
variables which interfere with the comparison we are attempting to make
p-value
the probability that a result was due to chance
Is rabies a disease that can be explained with a deterministic model?
yes
What kind of disease are best explained with multifactorial models?
complex (ex: osteoarthritis)
What infectious disease stage poses greatest risk to susceptible members of a population?
pre/sub clinical
Which of the following is correct?
C) Cohort studies are more powerful than cross-sectional studies
Are we worried about recall bias in prospective or retrospective studies?
retrospective
Does loss to follow-up occur with prospective or retrospective studies?
prospective
In which studies can we make a temporal association between exposure and outcome - prospective or retrospective?
prospective
